I have sailed 2x with the upgraded voucher...all I had to do was connect.
I'm not sure what you mean by "on sale", but if you mean the *real* on sale (i.e., $10 instead of $10/day) then that is what I used. I'm sure the other voucher (without the pricing mistake) works exactly the same. In fact, if you call X and ask what you have, they'll just say Premium.
There were some CC posts that indicated you needed to go to the iLounge, but myself - and others - who used the voucher didn't have to do anything.